1. Field of the Invention
The invention disclosed herein relates generally to a method and apparatus for converting linear reciprocating motion to rotary motion and vice-versa, and more particularly the present invention relates to a powertrain mechanism for converting reciprocating motion of a piston to rotary motion of a shaft and vice-versa.
2. Background of the Prior Art
Internal combustion engines, since the invention of such engines, have utilized a piston-crank mechanism as a basic power conversion mechanism of their powertrains. At the present time, a piston-crank mechanism is mostly used for such conversion. However, such mechanism requires a heavy connecting rod that, due to its lateral motion, generates piston side forces and complicated movement rendering engine balancing difficult. For a 4-stroke engine, a separate camshaft and associated gear train are required to operate inlet and exhaust valves. Various forms of piston-cam assembly powertrains have been introduced as an alternative to the piston-crank assembly powertrain. However, such piston-cam assembly powertrains have not achieved significant improvement over piston-crank assembly powertrains. Therefore, there remains a need for a piston-cam mechanism to convert linear reciprocating motion to rotary motion in a simple fashion while achieving reduction of shaft rotational speed without reduction gears.
It is an object of the invention to enable a piston-cam assembly powertrain that avoids the disadvantages of the prior art.
It is another object of the invention to provide an improved method and piston-cam assembly powertrain for converting the oscillating motion of a piston to the rotary motion of a shaft, and vice versa.
It is yet another object of the invention to provide a method for generating a multi-lobe cam profile for use in a piston-cam assembly powertrain.
It is still yet another object of the invention to provide a piston-cam assembly powertrain with fewer moving parts and less engine friction loss than previously known powertrains.
It is still even yet another object of the invention to provide a piston-cam assembly powertrain having no fixed connection between the connecting rods and the cam or cam shaft.
It is a further object of the invention to provide a piston-cam assembly powertrain that maintains the connecting rods in an orientation that substantially coincides with the centerline of its associated cylinder during the full stroke of the piston.
It is still yet a further object of the invention to provide a four-stroke engine that is operable without a separate camshaft and/or gear train to operate inlet and exhaust valves.
In accordance with the above objects, an improved method and piston-cam assembly powertrain are provided for converting the oscillating motion of a piston to the rotary motion of a shaft, and vice versa. A basic mechanism of the present invention consists of a rocking yoke assembly that oscillates about its middle point to rotate a multiple-lobe cam. The mechanism is so constructed that cam followers at both ends of the oscillating yoke make contact with the surface of the multiple-lobe cam. When the rocking yoke is oscillated it causes rotation of the camshaft. Alternatively, the rotating cam can cause oscillation of the rocking yoke. The multiple-lobe cam is formed of two identical facing plates having a gap between them defining an annular groove, the groove having sufficient width to accommodate the rocking yoke assembly between such cam plates with a pivoting bearing riding within such annular groove. Two connecting rods link cam followers at the ends of the rocking yoke to two pistons within two parallel cylinders to form a piston-cam assembly powertrain. A number of rocking yoke assemblies consisting of two parallel cylinders can be arranged around the camshaft in rows and/or columns for obtaining required power output.
The various features of novelty that characterize the invention will be pointed out with particularity in the claims of this application.